TEEN-heartthrob Justin Timberlake is just 21 years old, but his life is at a crossroads.He’s said bye bye bye to *NSYNC (at least for now); he and Britney Spears have gone their separate ways, and this Tuesday he puts it all on the line with a solo album.

Getting to know Timberlake as a person is harder than getting to know his music. In this interview, he guarded his words and only got comfortable toward the end of the conversation.

When asked about his kiss-and-tell indiscretion during an interview with Hot 97, Timberlake said he and Spears did share bedroom intimacy. Knowing he goofed, Timberlake added, “I’m in so much trouble.”

“I’d like to clear that up,” Timberlake told The Post.

“That was a situation where I didn’t want to seem like an ass on the radio, so I played along with Star [the interviewer]. I didn’t take it that seriously, and I made a joke on air. I’m glad to make any public apology that needs to be made. I never would disrespect somebody – especially somebody I was with for four years.”

As for other women in this eligible young bachelor’s life – he’s been linked to actress Alyssa Milano – he played coy.

“Women are great,” he said. “You want to know who I’m seeing?’ “

“Yeah.”

“You really want to know?” he teased.

“Go ahead.”

“Her name is ‘Justified.’ “

Timberlake admitted the geekiness of that exchange, but it was a clever way to change topics. In conversation, he lived up to his reputation as one of the sharpest pencils in the boy-band box.

Post: At the listening party for your album the other night, you didn’t look happy. What was wrong?

Timberlake: I don’t like listening to myself, and I was trying to get other people’s honest reaction to it.

Post: What did you find out?

Timberlake: People were pretty positive. That was cool.

Post: Of all the music played at the party, the one song that seemed to get everyone’s attention was “Right for Me.”

Timberlake: Yeah, that’s the one I do with Bubba Sparks. It’s raw. It’s just a beat-box, vocal-percussion groove. If you listen closely to the melody, you hear that it’s really honky-tonk. I think it stands out, too.

Post: On this album, you wrote every track. Can we assume the sentiments we’re hearing are the real you?

Timberlake: Absolutely, completely. But the cool part about music is that anybody listening can interpret what I wrote in terms of their own life.

Post: Is this album about your life?

Timberlake: About half of the album is autobiographical; the other half is made up of experiences. I think every artist has to reveal little bit of their personal baggage on a record, but sometime when you are being creative, you take on a role. It’s really up to the listener to put their spin on it.

Post: Is there a song on this album about a certain ex-girlfriend?

Timberlake: I wrote these songs from my heart, and people will take what they want from them.

Post: Is success important?

Timberlake: Listen, nobody does an album and says, “I hope this goes straight to No. 2.” I’m ambitious, I have goals and big plans, but at the same time, I know this is my first album. I don’t have any expectations.

Post: You really consider this your first album?

Timberlake: Yeah, I do. I was Justin before *NSYNC was *NSYNC. That’s why this is my first album.

Post: Was that a shot at *NSYNC?

Timberlake: I’d never knock anything *NSYNC does. I like what we do as a group, but *NSYNC doesn’t work without all of us – our individuality is our appeal. People are used to seeing me up front in *NSYNC, but I’m only one-fifth of the band. That’s the difference: This is 100 percent me.

Post: Is 100 percent addictive?

Timberlake: To say I’m not going to do another solo album would be stupid. I’m definitely going to do another one. Just like we are going to do another *NSYNC record.

Post: It doesn’t have to be one or the other?

Timberlake: There’s no reason my solo career and *NSYNC can’t co-exist in the same universe. *NSYNC is in no danger.

Post: So from what you say, this hiatus is a break, not a breakup.

Timberlake: The break we’re on was a conscious move. We all wanted to do it, and we were ready to do it. Performing at stadiums every night for 50,000 fans takes a little out of you. I was 14 when we started, and we’ve been touring for the last seven years. The time was right; we were all in the same zone. This album is what I wanted to do.

Post: At your listening party, somebody said to me, “This is the record Michael Jackson should have made.” What do you say to that?

Timberlake: You can’t compare this to “Invincible.” They are two very different albums. Michael Jackson is a legend. I’m not. I haven’t earned that. You can say all kinds of crazy stuff about Michael, but never forget, he’s a legend. It’s undeniable. I’m a huge fan of his. The comparisons are flattering, but I don’t see it.

Post: What about the hat thing on MTV’s Video Music Awards? Was that an homage to Jackson?

Timberlake: I’m a huge Fred Astaire fan. I love Gene Kelly and Frank Sinatra. They all used the hat. At the VMAs, I was trying to do my version of Frank Sinatra, so when everybody thought I was copying Michael Jackson, I never saw that coming.